In the programming of a xn-bit memory, such as an n-bit tunnel junction MRAM memory or the like, there is a need for n-digit line currents I, or `n` wordline currents I, or `n` bitline currents I, where `n` is the number of bits in a word, e.g. 16, 32, 64, etc. The total programming current of `n` digitlines adds up to nI current which is an unacceptable level. For example, in a 256.times.16 bit memory, the programming of a 16 bit word requires 16 bitline currents, or 16I, to flow from the current supply. When 16I current flows through the current supply lines, which are made up of metal and vias connecting layers of metal together, the vias become prone to electromigration damage, or migration of the metal, due to the excessive current flow.
Accordingly it is highly desirable to provide apparatus which overcomes these problems and which is inexpensive and easy to install and use.